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Author Topic: GMaj2 blown fuse  (Read 15631 times)

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rnolan

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GMaj2 blown fuse
« on: Time Format »

Hey ADAers, Mikes GMaj2 has blown the fuse in its power supply, we pulled it (the fuse) out on Sunday at rehearsal  :facepalm: (crap TCs' are difficult to open up  :dunno: , you have to take off the jack mounting nuts... and have all the special screwdriver bits (ahh but I have a few of them  :whoohoo!: who said buying tools was stupid.. )), then he used my (MP-2) guitar rig  >:D , so it didn't spoil they afternoon... (I think Mike likes the MP-2 triggered Wah.. LoL).  So he put a new fuse in today, blew straight away  :facepalm: crap.... He's looking into sending it to the TC tech support in Sydney (it's well out of warranty so this could be expensive, IF they even know what they are doing.. I suspect they'll just farm it out  :dunno: , I could be wrong).
Anyway, any ideas guys ??
So it's where the jug (IEC) lead comes into the unit, there's a small transformer and circuit board, the blown fuse is next to the transformer.
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #1 on: Time Format »

Does it have a switching PSU?
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Iperfungus

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Re: GMaj2 blown fuse
« Reply #2 on: Time Format »

No...these units have internal power supply.

Looks like a short circuit somewhere...transformer maybe?
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #3 on: Time Format »

Ok but it still can be a switching PSU,does it work on a wide range of input voltages?
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Iperfungus

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Re: GMaj2 blown fuse
« Reply #4 on: Time Format »

Ok but it still can be a switching PSU,does it work on a wide range of input voltages?

Yes, you're right MJMP.
100-240 VAC - 50-60 Hz 15W
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rnolan

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Re: GMaj2 blown fuse
« Reply #5 on: Time Format »

Hey MJMP, yes is switching PSU, just plug in a jug (IEC) lead it does the rest no matter what country/power supply (ish). Could it be a diode (gone) in the rectifier circuit ? Apart from the fuse all else looks ok  :dunno: .
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #6 on: Time Format »

Could be you can always check them out if your meter has a diode check.
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rnolan

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Re: GMaj2 blown fuse
« Reply #7 on: Time Format »

Hey MJMP, I'm pretty sure it does have a diode check, will give that a go, anything else it might be ?  We were running off a generator the last time it worked..
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #8 on: Time Format »

Could also be one of the switching transistors or mosfet's that stays on (busted) which also results in a blown fuse.

Is it a separate pcb (the PSU)? Sometimes these are off the shelf PSU they stick in there for easy repair. I repaired an axefx once that way, just bought a new one from mouser and it was fixed. If not sure, take a pic.
« Last Edit: Time Format by MarshallJMP »
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MikeB

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Re: GMaj2 blown fuse
« Reply #9 on: Time Format »

Yep, it's a separate pcb.   It would be great if I could do an easy fix because the agent wants $50 plus return postage just to look at it. attaching pics. Please let me know if you need more detail of close ups.
Thanks,
Mike

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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #10 on: Time Format »

Sorry Mike, seems I missed your post.I had a look around and can't find it for sale at mouser or farnell. It seems TC sells them for around 85 AU$ so maybe you can order one from them.You need a JKS020Q1.

I did found the schematic of it in case you want to poke around yourself.

http://www.dirk-hendrik.com/temp/TC_electronic_SMPS%20JKS020Q1.pdf

I also found it here  http://www.fullcompass.com/prod/099092-TC-Electronic-7E50000101

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MikeB

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Re: GMaj2 blown fuse
« Reply #11 on: Time Format »

No worries. I know you have a pretty full dance card.   Thanks for the links. I'll have to see what the shipped price is on this and then compare it with how much beer it will cost me to get my electronic engineer mate to have a go at the blown one.
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #12 on: Time Format »

Ok let me know if I can help out with something.
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MikeB

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Re: GMaj2 blown fuse
« Reply #13 on: Time Format »

So,
My mate, Glenn, has come around and had a poke around.  He found that one of the MOSFETs had blown (Q2 on the schematic).
The part number listed on the schematic is 2SK2526 or 2SK1637.  Mouser had an equivalent part (searching for 2SK1637) with a manufacturers part number of STF3N62K3.
They had this part listed at $1.87 Australian but with $24 postage.  Then I had another poke around online and found through RS Online the same part that I can get delivered for $4.88 (for a pack of 5).
I'd be grateful if you could confirm that these two parts are interchangeable (see attached datasheets).  I have ordered it in any case as the gamble of $4.88 is one that I'm prepared to take.
Glenn also found that the D9 diode was blown.  The schematic just lists this part as "small signal silicon with 0.6VTH".  I have bought a packet of 5 diodes (for 80c) that are labelled as "1N914/1N4148/BAW76 D035".  Will one of these do the trick?

I do appreciate any input you can give me on this.  Thanks.

Cheerio,
Mike
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MarshallJMP

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Re: GMaj2 blown fuse
« Reply #14 on: Time Format »

From what I can tell they look good, they even have a bit more power. (45Wvs 35W)

A 1N4148 is a small signal diode, so should do the trick. Let's hope nothing else is busted that could have caused the Q2 to blow up itself.
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